Conclusion

An in-depth understanding of the cells that make up the various plant parts, the structures of those cells, and the contents of the cell is critical to conducting a microscopic evaluation of both known and unknown plants. The following chapters describe in detail the development of cells into their respective tissues and plant parts, as well as their diagnostic application when a microscopic evaluation is conducted.

Transverse Sections

Longitudinal Sections

Transverse Sections

Longitudinal Sections

Root Secondary Microscopic

FIGuRE 7.21 Fibers with and without slit-like pits shown in transverse and longitudinal sections. (a) Secondary xylem showing fibers with pits of Berberis nervosa root (transverse section); (b) secondary xylem showing fibers with pits of Berberis nervosa root (longitudinal section); (c) bundles of fibers without pits in secondary phloem of Pausinystalia yohimbe bark (transverse section); (d) fibers without pits in secondary phloem of Pausinystalia yohimbe bark (longitudinal section); (e) bundles of fibers with slit pits of Uncaria tomentosa bark (transverse section); (f) bundles of fibers with slit pits of Uncaria tomentosa bark (longitudinal section). (Images courtesy of Prof. Dr. Reinhard Länger, AGES PharmMed, Vienna, Austria.)

e illustration image illustration image

Brachysclereid
50 |um

FIGURE 7.22 Types of sclereids. (a) Grouped sclereids of Viburnum prunifolium bark (transverse section); (b) grouped sclereids of Viburnum prunifolium bark (transverse section); (c) brachysclereid of Scutellaria baicalensis root (transverse section; (d) brachysclereid of Scutellaria baicalensis root (transverse section)). (Images courtesy of Prof. Dr. Reinhard Länger, AGES PharmMed, Vienna, Austria.)

Macrosclereids

FIGuRE 7.22 (continued.) Types of sclereids. (e) Macrosclereid layer of Silybum marianum cypsela (longitudinal section); (f) macrosclereid layer of Silybum marianum cypsela (longitudinal section); (g) macrosclereid layer of Illicium verum seed testa (longitudinal section); (h) macrosclereid layer of Illicium verum seed testa (longitudinal section);. (Images courtesy of Prof. Dr. Reinhard Länger, AGES PharmMed, Vienna, Austria.)

FIGURE 7.22 (continued.) Types of sclereids. (i) Astrosclereid of Illicium verum columella (longitudinal section); (j) astrosclereid of Illicium verum columella (longitudinal section). (Images courtesy of Prof. Dr. Reinhard Länger, AGES PharmMed, Vienna, Austria.)

Table 7.3 Most Common Forms of Sclereids

Type

Characteristics

Brachysclereid

More or less isodiametric; most common form of sclereid (Figure 7.22c and d)

Macrosclereid

Rod shaped and often found in layers one or two cells thick; frequently occurring as the external boundary tissue in seed coats (Figure 7.22e-h)

Astrosclereid

Highly branched, with long arms (Figure 7.22i and j)

Table 7.4 Cell Types, Their Location, and Primary Functions

Type

Characteristics

Location

Functions

Collenchyma

Elongated with unevenly thickened cell walls

Beneath epidermis; along veins in some leaves

Structural support of primary plant body

Companion cell

Generally elongated

Phloem

Functions in metabolism of sieve tubes

Fibers

Generally long with thickened cell walls

Xylem, phloem, barks, leaves along the veins, fruits, etc.

Structural support

Parenchyma

Variably shaped; commonly polyhedral

Throughout plant

Respiration, photosynthesis, storage, conduction, regeneration

Sclereids

Variably shaped; generally shorter than fibers; thickened walls

Throughout plant

Mechanical, protective

Sieve cell/sieve tube

Elongated, tapered; often associated with pores

Phloem

Primary nutrient-conducting cell in gymnosperms and lower vascular plants

Tracheid

Elongated, tapered; thickened cell walls

Xylem

Primary water-conducting cell in gymnosperms; tissue dead and hollow at maturity

Vessels

Elongated; generally shorter than tracheids; thickened cell walls

Xylem

Primary water-conducting cell in angiosperms; tissue dead and hollow at maturity

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